Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w=map(int,input().split())
s=[list(input()) for i in range(h)]
cntW=0
for i in range(h):
  for j in range(w):
    if s[i][j]=='.':
      cntW+=1
dist=[[-1]*w for i in range(h)]
dist[0][0]=0
q=[(0,0)]
q=deque(q)
dx=[1,0,-1,0]
dy=[0,1,0,-1]
while q:
  y,x=q.pop()
  for i in range(4):
    ny,nx=y+dy[i],x+dx[i]
    if 0<=ny<h and 0<=nx<w and dist[ny][nx]==-1 and s[ny][nx]=='.':
      dist[ny][nx]=dist[y][x]+1
      q.appendleft((ny,nx))
if dist[-1][-1]==-1:
  print(-1)
else:
  print(cntW-dist[-1][-1]-1)